Where is the "clutch feature"? How do I active the pedals?
smarTrike's classic trikes are equipped with a 2-mode pedaling system. When your child is unable to to pedal, have them rest their feet on the footrest with the clutch open. This will disengage the pedals from affecting the ride.
You can check out this video for a live demonstration: https://youtu.be/uy_2QTrfJbs?t=8m19s
In order to lock it securely, you will have to push the clutch in towards the wheel so it lies flush against it (rather than looking like it is popped outwards). This activates the pedals, and will enable your child to pedal on their own.